6=x
4 2

4x=12
4 4

x=3

Clarify your question please.

I'm not sure there's a question here, but it looks like the OP is trying to say this:

Given



\frac 6 4 = \frac x 2


Cross-multiply:

4x = 12

Divide boith sides by 4:

x = 3.

I see it now! Though that isn't much of a question indeed :(